Study of Noise, Hearing Impairment and Hypertension in Egypt

Abstract

This study included 295 workers of Assiut Generation Station (Upper Egypt). Two hundred and twenty-one of the workers were exposed to different levels of noise (80 to 107 dBA) and the remaining 74 were used as a control group. There were no significant differences in risk factors viz age, duration of work, body mass index, weight, height, smoking, and previous work as determined by a questionnaire. The relationship between occupational exposure to noise, the degree of hearing loss and hypertension was determined. The results showed that there were statistically significant differences between the average hearing threshold levels of the two groups (P<0.01) which were more in those workers exposed to noise than in the control group. The mean systolic and diastolic blood pressures were also statistically significantly different in the two groups (P<0.001) and they were positively correlated (P<0.001) to the percentage of impairment of the whole body at 4 and 6 kHz, and hearing disability at 0.5, 1, 2, and 3 kHz. Stepwise multiple regression analysis revealed that age, noise level and body weight could each be used as a predictor of hypertension. A predictive formula was derived between the amount of hearing loss and blood pressure in the subjects exposed to occupational noise. Ann Saudi Med 1994;14 (4) Noise can be a health hazard in two main ways: it can damage hearing and it can affect various body systems. The auditory effects of noise have been documented and evidence has been accumulated regarding the cardiovascular effects of noise.1 Noise was recognized by the World Health Organization (WHO) in 1983 2 as one of a number of possible exogenous factors in the pathogenesis of essential hypertension. Von Eiff et al.3 found a significant increase in the incidence of hypertension among people living and working in proximity to aircraft and automobile traffic.The correlation between the degree of hearing impairment and elevation of systolic and diastolic blood pressure has not yet been established. Early screening surveys 4 on middle age population could not find such correlation, while a recent study 5 found a statistically significant positive correlation between the two variables among retired metal workers who had been exposed to noise -84 dBA-for 30 years or longer.The aim of this work was to investigate the relationship between elevation of hearing threshold and blood pressure (systolic and diastolic) among subjects exposed to various noise levels; and at the same time considering the effect of other variables such as duration of exposure and age on such relationship. Material and MethodsThis study was conducted in Assiut Electricity Generation Station (EGS) in Assiut, Egypt. A) Subjects: 221 employees exposed to noise in the station were the study subjects. None of the employees was excluded unless he had severe deafness resulting from a known cause other than noise or suffered from hypertension (pressure more than or equal to 160/95 mm/Hg) or there was a history of antihypertensive medication prior to work i...